Regarding the problems Rolf has had with 5,6x61 SEvH, this caliber has a reputation for Secondary Explosion Effect, (S.E.E.). The case is very large for the bore size so it's said to be overbored. Some of the early recommended powders do not seem to have filled the case well. It seems Rottweil R905 is no longer recommended.

Lutz Moeller recommeds, in connection with this cartridge especially, to only choose powders that ideally fill the case 100% (or better still lightly compressed), but never less than to the shoulder base. You shouldn't exceed published data to achieve this, obviously.

S.E.E. causes are not precisely known, but for instance, one theory is that there's a partial combustion and then a short hesitation that releases certain explosive gases; these are then ignited in the secondary explosion. Because these gases release much more energy, the rifle blows. Other complications that can cause this too-weak initial combustion can be using a standard when a magnum primer was specified, or a too weak firing pin spring.

Wild und Hund in 4/1986 stated that new data using Hodgdon H870 cured these early problems. (It says, in part, "Bei diesen Pulversorten wird übrigens eine Ladedichte von 100 Prozent erreicht. Es ergaben sich in dieser Zeit keine Beanstandungen"). However, H870 is now discontinued and it also created certain fouling problems in this caliber for which a Lee Factory Crimp die was only a partial cure for me.

I now only use Hodgdon H4831SC using data from Jeff Munnell's published article in Reloader magazine.